1. Field of the Invention
The present invention relates to wireless IC devices, and, more particularly, to a wireless IC device including a wireless IC chip used for an RFID (Radio Frequency IDentification) system.
2. Description of the Related Art
In recent years, as a product management system, an RFID system has been developed in which a reader/writer for generating an induction field communicates with an IC chip (hereinafter also referred to as an IC tag or a wireless IC chip) attached to a product or a case in a non-contact manner so as to obtain predetermined information stored in the IC chip. As a wireless IC device including an IC chip, a module for a non-contact IC medium disclosed in Japanese Unexamined Patent Application Publication No. 2003-331246 is known.
The module for a non-contact IC medium is formed by an LSI, a loop antenna, and a capacitance element. A resonance circuit is formed using the inductance of a line of the loop antenna and the capacitance of the capacitance element, and performs impedance matching between the loop antenna and the LSI.
However, in the module for a non-contact IC medium, in order to obtain an inductance value required for the impedance matching between the loop antenna and the LSI, it is necessary to adjust the length of the loop antenna. Accordingly, the length of the loop antenna is changed in accordance with the input impedance of a used LSI, and the size of the module itself and an antenna radiation characteristic are changed.